It's the perfect way to do it. You provide a service for free to let people see how much simpler their lives could be with your product and when you have a high enough ratio of people that can't live without it, you begin to charge for it. You put the rumors out either from the beginning or in enough time to see how many people you will lose if you really do it and when you are fine with the final numbers, you start charging. It's how Microsoft became MICROSOFT. They gave away Windows for free to so many businesses, that it became the default system and everyone had to fall in line.